Allophane and Imogolite

This chapter deals with allophane and imogolite in soils derived from volcanic ash, and in weathered pumices and Spodosols. Syntheses of allophane, imogolite, and their precursors have thrown light on their genesis, structure, and morphology, and also on the reactions of aluminum with silicic acid in soil solution. Important information about the morphology and internal structures of allophane and imogolite is obtained from the use of a high-performance electron microscope. Allophane and imogolite develop variable electric charge on their surfaces. Its development is influenced by pH, by the nature and concentration of cations and anions in solution, and by temperature. The physical and engineering properties of soils having a high allophane and imogolite content are unique. The acquired knowledge has provided a basis for interpreting their effect on chemical and physical properties that pose a number of problems in the practical management and use of soil systems.